BIOL 2021 Lecture Notes - Lecture 9: Lipid Bilayer, Supramolecular Assembly, Membrane Protein
Document Summary
Moderates fluidity of membranes both increases and decreases: cholesterol in membranes decreases fluidity because it is rigid, prevents crystallization (making solid) of fatty acyl side chains by fitting between them. Biological membranes contain proteins as well as lipids: Rest is lipid or carbohydrate; supramolecular assembly of lipid, protein and carbohydrate. Two classes of membrane proteins: integral membrane proteins, peripheral membrane proteins. Transporters moving molecules into or out of cells or cell membranes. Receptors transmitting signals from outside of the cell to the inside. Barrel-shaped membrane protein that is made up of antiparallel -strands with hydrophilic (interior) and hydrophobic (facing lipid tails). So far found only in outer membranes of gram-negative bacteria, cell wall of. Gram-positive bacteria, and outer membranes of mitochondria and chloroplasts. Can cross the membrane once or many times and have multiple transmembrane segments. In humans, 27% of all proteins have been estimated to be alpha-helical membrane proteins.
